A crank of length 190mm is initially at 65 degree above the horizontal, and rotates through 35 degree towards the horizontal. A vertically downward force of 160 N acts on the outer end of the crank. Calculate the work done by the force.

Answer 1

φ is the angle between the force ‘F’ and the crank ‘r’
φ₁=180°-90°-65° =25°
φ₂=180°-90°-30° =60°

The work is
dW= M•d φ=F•r•sinφ•dφ
W=∫ F•r•sinφ•dφ =-F•r•cosφ |₂₅⁶⁰= - =160•0.19• (0.5-0.9)=12.16 J